Improvement in countersink and bit



atea .salati f gaat entre WILLIAM A. CLARK, or WOODBRIDGE, CONNECTICUT.

12mm Para: No. 93,807, data August 17,1869.

nurnovnnmn'r IN coUN'rnRsrm: AND Brr.

The Schedule referred to in these Letters Patent and making part of the name To all. whom'fit 'ma/y concern.-

Be it known that I, WILLIAM A. CLARK, of Wood'-v bridge, in the county of New Haven, and State of Connecticut, have invented a new Improvement in Combined Gountersink and Bit; and I do hereby declare the following, when taken .in connection with the accompanying drawings, and the letters of reference marked thereon, to be a full, -clear, and exact description of the same, and which said drawings constitute part of this specification, and represent, in-

Figure 1, a side view, looking -toward the edge of the spur; y

Figure 2, the same turned one-fourth around; Figure 3, the same turned another fourth around;

4 Figure 4, the bit detached;

of the counter-bore will always conform to the throat v or twist of the bit.

Second, in forming the counterbore or countersink v -with a plug-cutter, in one and the same piece.

.To enable others skilled in the art to construct and use my improvement, I will proceed to describe the same as illustrated in the accompanying drawings.

A is a boring-instrument, commonly calleda gimlet bit.

The part B, extending from the bit A to the shank C, is of an equal diameter, the bit'being tapering, as in conimon gimlet-bits, and theshank so as to be itted to a common brace.

D is the counterborc, which consists 0f a cylinder, formed so as to pass on to thc paItB; and at its lower end a cutter, ,is formed, and a spiral throat, d, extending from the cutter around the cylinder D, the twist conforming nearly to thatofthe twist ofthe bit; and upon the edge of the throat, opposite the cutter a, is formed a spur, j, to cnt in advance of the cutter a. v

The shape of the cutter a, is such that it will cut a seat for the screw-head to set into, in similar manner as common conntersinks.

The cylinder D is set on 'overthe bit, as seen in iig 1 .set-screw, E, passes, through the cylinder, into the spiral'groove b, (see fig. 4,) so that the throat d,

of the cutter u, will conform to the throat or twist of the bitbelow, as seen in iig. 1. This forms a channel for the pa'ssage of the chips both' from the bit and counterbore, and the groove b, conforming vt0 the twist of the bit, will always hold the throat of the counterbore in the same. relative position, at whatever height it is placed from the point.;

' Over the cylinder is arranged a stop, Gr, set upon the cylinder D, so as 'to arrest the operation of the-bit.,

when therequired depth"=is bored, the guidepassing over the throat, so asin Vno way to stop the throat.

It will be observed, that for dif'erentsized screws, different-sized bits will be required, and different-sized counterbores may be applied to the said instrument.

As a plug-cutter-that is, an instrument for cuttinga plug to ill in overthe screw-head-I construct upon the other end of the cylinder Da cutter, L, in the form of a segment o f a. circle, the inner diameter of which corresponds t0 the diameter of the cutter-end 'of the cylinder.

' To use this cutter, I-inveit the cylinder, as seen in fig. 6, placing it upon the same bit, and changing the set-screw E from the 'position seen in iig. 5 to the other end, as seen in fig. 6. Then the plug-cutter is used in like manner as other plug-cutters.

Having fully described my invention,

What I claim as new and useful, and desire to secure by Letters Patent, is-

In combination withthemounterbore, made adjustable in a hit, the plug-cutter L, formedinone andthe same'piece with the eonnterbore, and so as tobeap plied to the hit, snbstantially'as set forth.

WML., VA.I CLARK.

Witnesses: l

A. J'. TLBBITS,

J..H. SHUMWAY. 

